Highly Conductive Boron Nanotubes: Transport Properties, Work Functions, and Structural Stabilities

Bezugly, Viktor,Kunstmann, Jens,Grundkö,tter-Stock, Bernhard,Frauenheim, Thomas,Niehaus, Thomas,Cuniberti, Gianaurelio American Chemical Society 2011 ACS NANO Vol.5 No.6

<P>The transport properties, work functions, electronic structure, and structural stability of boron nanotubes with different lattice structures, radii, and chiralities are investigated theoretically. As the atomic structure of boron nanotubes and the related sheets is still under debate, three probable structural classes (nanotubes derived from the α-sheet, the buckled triangular sheet, and the distorted hexagonal sheet) are considered. For comparison with recent transport measurements [<I>J. Mater. Chem</I>. <B>2010</B>, <I>20</I>, 2197], the intrinsic conductance of ideal nanotubes with large diameters (<I>D</I> ≈ 10 nm) is determined. All considered boron nanotubes are highly conductive, irrespective of their lattice structures and chiralities, and they have higher conductivities than carbon nanotubes. Furthermore, the work functions of the three sheets and the corresponding large-diameter nanotubes are determined. It is found that the value of the nanotubes obtained from the α-sheet agrees well with the experiment. This indirectly shows that the atomic structure of boron nanotubes is related to the α-sheet. The structural stability of nanotubes with diameters > 2 nm approaches that of the corresponding boron sheets, and α-sheet nanotubes are the most stable ones. However, for smaller diameters the relative stabilities change significantly, and for diameters < 0.5 nm the most stable structures are zigzag nanotubes of the buckled triangular sheet. For structures related to the distorted hexagonal sheet the most stable nanotube is discovered to have a diameter of 0.39 nm.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-6/nn201099a/production/images/medium/nn-2011-01099a_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn201099a'>ACS Electronic Supporting Info</A></P>

Structural properties of water around uncharged and charged carbon nanotubes

Mozaffar Ali Mehrabian,Amir Reza Ansari Dezfoli,Hassan Hashemipour Rafsanjani 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.3

Studying the structural properties of water molecules around the carbon nanotubes is very important in a wide variety of carbon nanotubes applications. We studied the number of hydrogen bonds, oxygen and hydrogen density distributions, and water orientation around carbon nanotubes. The water density distribution for all carbon nanotubes was observed to have the same feature. In water-carbon nanotubes interface, a high-density region of water molecules exists around carbon nanotubes. The results reveal that the water orientation around carbon nanotubes is roughly dependent on carbon nanotubes surface charge. The water molecules in close distances to carbon nanotubes were found to make an HOH plane nearly perpendicular to the water-carbon nanotubes interface for carbon nanotubes with negative surface charge. For uncharged carbon nanotubes and carbon nanotubes with positive surface charge, the HOH plane was in tangential orientation with water-carbon nanotubes interface. There was also a significant reduction in hydrogen bond of water region around carbon nanotubes as compared with hydrogen bond in bulk water. This reduction was very obvious for carbon nanotubes with positive surface charge. In addition, the calculation of dynamic properties of water molecules in water-CNT interface revealed that there is a direct relation between the number of Hbonds and selfdiffusion coefficient of water molecules.

$TiO_2$ Nanotubes Preparation and Its Formation Mechanism

Kang, Young-Gu,Shin, Ki-Seok,Ahn, Sung-Hwan,Hahm, Hyun-Sik The Korean Society of Applied Science and Technolo 2010 한국응용과학기술학회지 Vol.27 No.4

There has been a controversy on the formation mechanism of $TiO_2$ nanotubes. This study was conducted to elucidate the formation mechanism of $TiO_2$ nanotubes. $TiO_2$ nanotubes were prepared by a hydrothermal method. $TiO_2$ nanotubes formation mechanism was investigated by controlling the formation time. It was found that $TiO_2$ nanotubes were formed by growing, not by wrapping of sheets. The phase structure of hydrogen titanate nanotubes was different from that of $TiO_2$ nanotubes. It is important to wash the sodium titanate nanotubes with an acidic solution to get hydrogen titanate nanotubes and then to calcine the hydrogen titanate nanotubes around $400^{\circ}C$ to obtain $TiO_2$ nanotubes.

TiO2 Nanotubes Preparation and Its Formation Mechanism

( Young Gu Kang ),( Ki Seok Shin ),( Sung Hwan Ahn ),( Hyun Sik Hahm ) 한국유화학회 2010 한국응용과학기술학회지 Vol.27 No.4

There has been a controversy on the formation mechanism of TiO2 nanotubes. This study was conducted to elucidate the formation mechanism of TiO2 nanotubes. TiO2 nanotubes were prepared by a hydrothermal method. TiO2 nanotubes formation mechanism was investigated by controlling the formation time. It was found that TiO2 nanotubes were formed by growing, not by wrapping of sheets. The phase structure of hydrogen titanate nanotubes was different from that of TiO2 nanotubes. It is important to wash the sodium titanate nanotubes with an acidic solution to get hydrogen titanate nanotubes and then to calcine the hydrogen titanate nanotubes around 400℃ to obtain TiO2 nanotubes.

TiO2 Nanotubes Preparation and Its Formation Mechanism

강영구,신기숙,안성환,함현식 한국응용과학기술학회 2010 한국응용과학기술학회지 Vol.27 No.4

There has been a controversy on the formation mechanism of TiO2 nanotubes. This study was conducted to elucidate the formation mechanism of TiO2 nanotubes. TiO2nanotubes were prepared by a hydrothermal method. TiO2 nanotubes formation mechanism was investigated by controlling the formation time. It was found that TiO2 nanotubes were formed by growing, not by wrapping of sheets. The phase structure of hydrogen titanate nanotubes was different from that of TiO2 nanotubes. It is important to wash the sodium titanate nanotubes with an acidic solution to get hydrogen titanate nanotubes and then to calcine the hydrogen titanate nanotubes around 400℃ to obtain TiO2 nanotubes.

Highly Efficient Silver–Cobalt Composite Nanotube Electrocatalysts for Favorable Oxygen Reduction Reaction

Yu, Areum,Lee, Chongmok,Lee, Nam-Suk,Kim, Myung Hwa,Lee, Youngmi American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.48

<P>This paper reports the synthesis and characterization of silver cobalt (AgCo) bimetallic composite nanotubes. Cobalt oxide (Co3O4) nanotubes were fabricated by electrospinning and subsequent calcination in air and then reduced to cobalt (Co) metal nanotubes via further calcination under a H-2/Ar atmosphere. As-prepared Co nanotubes were then employed as templates for the following galvanic replacement reaction (GRR) with silver (Ag) precursor (AgNO3), which produced AgCo composite nanotubes. Various AgCo nanotubes were readily synthesized with applying different reaction times for the reduction of Co3O4 nanotubes and GRR. One hour reduction was sufficiently long to convert Co3O4 to Co metal, and 3 h GRR was enough to deposit Ag layer on Co nanotubes. The tube morphology and copresence of Ag and Co in AgCo composite nanotubes were confirmed with SEM, HRTEM, XPS, and XRD analyses. Electroactivity of as-prepared AgCo composite nanotubes was characterized for ORR. with rotating disk electrode (RDE) voltammetry. Among differently synthesized AgCo composite nanotubes, the one synthesized via 1 h reduction and 3 h GRR showed the best ORR. activity (the most positive onset potential, greatest limiting current density, and highest number of electrons transferred). Furthermore, the ORR performance of the optimized AgCo composite nanotubes was superior compared to pure Co nanotubes, pure Ag nanowires, and bare platinum (Pt). High ethanol tolerance of AgCo composite nanotubes was also compared with the commercial Pt/C and then verified its excellent resistance to ethanol contamination.</P>

Bending, buckling and vibration analyses of nonhomogeneous nanotubes using GDQ and nonlocal elasticity theory

Pradhan, S.C.,Phadikar, J.K. Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.2

In this paper structural analysis of nonhomogeneous nanotubes has been carried out using nonlocal elasticity theory. Governing differential equations of nonhomogeneous nanotubes are derived. Nanotubes include both single wall nanotube (SWNT) and double wall nanotube (DWNT). Nonlocal theory of elasticity has been employed to include the scale effect of the nanotubes. Nonlocal parameter, elastic modulus, density and diameter of the cross section are assumed to be functions of spatial coordinates. General Differential Quadrature (GDQ) method has been employed to solve the governing differential equations of the nanotubes. Various boundary conditions have been applied to the nanotubes. Present results considering nonlocal theory are in good agreement with the results available in the literature. Effect of variation of various geometrical and material parameters on the structural response of the nonhomogeneous nanotubes has been investigated. Present results of the nonhomogeneous nanotubes are useful in the design of the nanotubes.

Bending, buckling and vibration analyses of nonhomogeneous nanotubes using GDQ and nonlocal elasticity theory

S.C. Pradhan,J.K. Phadikar 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.2

In this paper structural analysis of nonhomogeneous nanotubes has been carried out using nonlocal elasticity theory. Governing differential equations of nonhomogeneous nanotubes are derived. Nanotubes include both single wall nanotube (SWNT) and double wall nanotube (DWNT). Nonlocal theory of elasticity has been employed to include the scale effect of the nanotubes. Nonlocal parameter, elastic modulus, density and diameter of the cross section are assumed to be functions of spatial coordinates. General Differential Quadrature (GDQ) method has been employed to solve the governing differential equations of the nanotubes. Various boundary conditions have been applied to the nanotubes. Present results considering nonlocal theory are in good agreement with the results available in the literature. Effect of variation of various geometrical and material parameters on the structural response of the nonhomogeneous nanotubes has been investigated. Present results of the nonhomogeneous nanotubes are useful in the design of the nanotubes.

TiO₂ nanotubes/carbon nanotubes for indoor CO₂ gas reduction

김현,양비룡 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

A manned spacecraft environmental control and life support system (ECLSS) is a group of systems that allow human to live in space for long term exploration. Generally ECLSS consists of several main components such as, atmosphere, water recovery and managements. In this study twisted TiO₂ nanotubes/carbon nanotubes were prepared and tested for different parts of the ECLSS. In first step photocatalytic oxygen generation using twisted TiO₂ nanotubes/carbon nanotubes with IrO₂ nanoparticles coated optical fibers will be performed. In second and third step CO₂ photoreduction and water purification systems using twisted TiO₂ nanotubes coated optical fibers will be developed and tested, respectively. In fourth step, air purification systems will be developed. In final step twisted TiO₂ nanotubes/carbon nanotubes coated optical fibers in cylinder type reactor will be employed to develop anti-contaminant and antibacterial systems.

Enhanced torsional stability of carbon nanotubes with tensile pre-strain

Jeong, B.W.,Kim, H.Y. North-Holland 2015 Physica E, Low-dimensional systems & nanostructure Vol.66 No.-

This work examines the torsional mechanical properties of single-walled carbon nanotubes with tensile pre-strains using classical molecular dynamics simulations. In particular, it is investigated how much the tensile pre-strains enhance the torsional stability of nanotubes, and how this enhanced torsional stability is dependent on the chirality of nanotubes. The observations reveal that the tensile pre-strains greatly enhance the torsional stability of nanotubes and the effects are strongly dependent on the degrees of tensile pre-strains and the chirality of nanotubes. The increase rates of torsional buckling moments are in proportion to the degrees of tensile pre-strains and much larger in zigzag nanotubes than in armchair nanotubes. In the case of zigzag nanotubes, the maximum increase rate of torsional buckling moment is 122.3% for the tensile pre-strain of 0.115. In addition, the tensile pre-strains also alter the torsional stiffness of nanotubes depending on the degrees of tensile pre-strains and the chirality of nanotubes.